This invention relates to a process for forming a multi-layer coating film which comprises an intermediate coating film, a metallic coating film and a clear coating film, and which has chipping-resistance and smoothness improved.
It has already been known to form, on exterior surfaces of automobile body etc., a multi-layer coating film by 3C1B method, i.e., by applying intermediate paint, metallic paint and clear paint in this order, and curing the resultant coatings simultaneously by heating. It is often seen that this multi-layer coating film is hit by gravels spattered by a running car, and thus partially peels off (which phenomenon is called xe2x80x9cchippingxe2x80x9d). In order to resolve this chipping, it has been proposed to place flexible coating film between coating film layers. This method is, however, undesirable since it increases the number of coating process steps.
The objective of this invention is to improve, without increasing the number of coating process steps, the chipping-resistance of a multi-layer coating film which is formed by 3C1B method with use of intermediate paint, metallic paint and clear paint.
As a result of assiduous study, the inventors of this invention have now found out that the above-mentioned objective is achieved when the intermediate paint contains 0.5 to 5 phr of flat talc powder of a specific size and has a total pigment content of 40 to 100 phr, and, thus, the inventors have completed this invention.
This invention relates to a process for forming a multi-layer coating film by applying, to a substrate, intermediate paint, metallic paint and clear paint by 3C1B method, which process is characterized in that said intermediate paint contains 0.5 to 5 phr of flat talc powder of a size of 0.5 to 10 xcexcm in longer direction and 0.01 to 1 xcexcm in thickness, and has a total pigment content of 40 to 100 phr.
In the following, the process of this invention for forming a multi-layer coating film is explained in more detail.